As host of the most-listened-to Top 40 morning show in America, Elvis Duran has a knack for discovering the next big thing.

“Back in the day, Mariah Carey came in here for her very ﬁ st on-air interview — she was just this nervous little girl,” he recalls. “But as I sat there and watched her talk, I knew she was going to be a superstar.”

He was right. For the past 18 years, Elvis has developed a talent for sniffing out future hit makers when interviewing them on his NYC-based radio program, Elvis Duran and the Morning Show. “Sometimes an artist will walk in, and you just know they’re going to be huge,” Elvis, 49, tells In Touch.

“Watching their careers grow is gratifying,” he adds. “It makes me feel like I have the best job in the world.”

Another of his accurate predictions: the rise of a surprisingly starstruck young artist named Lady Gaga.

“I [could tell] she had that engine that would never run out of gas,” says Elvis, adding that the singer — who grew up in NYC — was one of the most humble celebs he’s ever met.

“She walked in the studio and just froze,” he recalls. “She said, ‘When I was little I would listen to your show and dream of the day you would play my song — and now here I am,’” recalls Elvis. “She was overwhelmed.”

Elvis could relate: Growing up in Texas, he dreamed of one day hearing his own voice over the airwaves. “I was obsessed with radio as a kid,” he says. He got his foot in the door at a small Dallas radio station in the early ’80s; gigs in Atlanta and Houston followed before he landed his dream job at NYC’s Z100 in 1986.

While he’s been lucky enough to befriend tons of celebs over his long career, not every ﬁrst meeting has been a winner. “Janet Jackson had a team look under the toilet seats to make sure there weren’t any hidden cameras before her interview,” says Elvis. A young Christina Aguilera got “p--sed off ” when she didn’t get a McDonald’s breakfast before going on the air. But one of the worst celebrities he’s dealt with?

“Usher,” he reveals. “He’s one of the most talented people on the planet … But he was a little brat!”

Despite more than 30 years on the radio, workaholic Elvis — who’s also hosted music segments on Today and Entertainment Tonight and lives in NYC with his partner of three years, zookeeper Alex Carr, 33 — doesn’t plan on slowing down anytime soon.

“I’ll leave radio someday,” he predicts. “Right now I’m having the time of my life!”